The present invention relates to a controllable radial pump, in particular for feeding a cooling medium for a motor vehicle.
Radial pumps are frequently used in the motor vehicles for cooling of the motor. The cooling medium is fed usually through a closed cooling circuit. The corresponding vehicles are as a rule provided with a single mechanical pump which is driven by a belt from the motor and in this way provides the circulation of the cooling medium. The direct coupling of such a cooling medium pump to the motor as a result determines the fed cooling medium speed from the rotary speed of the motor and therefore the adjustability of the cooling medium circulation is substantially limited.
These radial pumps which are used as cooling medium pumps must be dimensioned so that when they operate in a low rotary speed region and at high motor loads, for example mountain travels with a trailer, they must still provide sufficient cooling. The cooling efficiency and thereby the drive efficiency of the cooling medium pump is then designed for the normal region too high, which leads to unnecessarily high energy consumption. The German patent document DE 30 07 640 discloses adjustable drives for motor vehicle-cooling medium pumps, in which a transmission is arranged between the crankshaft of the internal combustion engine and the shaft of the water pump. Furthermore, switchable visco-couplings and hydraulic drives are known which are arranged in this region and guarantee an adjustability of the cooling medium pump. All these drives are characterized by losses, they are expensive both because of the technique and their dimensions, and they are not useable in all vehicle classes.
A basically different possibility with respect to the adjustability of the cooling medium pumps is the use of motor-independent, electrically driven pumps. This however can not be realized for large vehicles, which require pump drive powers within the range of up to 1 kW, since this can lead to big and heavy electric motors and generators.
Accordingly, its an object of present invention to provide an adjustable radial pump for motor vehicles which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in an adjustable radial pump of this type, in which the adjusting device is operatively connected with a sleeve which is displaceable by the adjusting device over the pump vanes in an axial direction.
When the radial pump is designed in accordance with the present invention, volume stream of the medium to be fed, despite the direct drive from the motor, is adjustable independently from its rotary speed. This is made possible by the connection of the adjusting device with the sleeve arranged around the pump wheel, which is displaceable by the adjusting device over the pump vanes in the axial direction and thereby allows a variation of the size ratio of the pump chamber which receives the pump wheel.
In accordance with another feature of the present invention, the sleeve is cup-shaped and has a cup-bottom which is provided with slots for receiving the pump vanes. This makes possible a variation of the effective surface of the pump vanes variation
The coupling of the adjusting movement of the adjusting device to the temperature of the medium fed by the pump is especially advantageous. Thereby the adjusting device can be switched for adjusting the volume stream so that with the increasing temperature of the medium, an increasing high pump power is provided. Then for example with the use of the pump in the motor vehicles with a cooled motor, the pump power and the required cooling medium volume are low, which can lead to a fast reaching of the optimal motor operation temperature. With higher loads and therefore higher motor or cooling medium temperatures, to the contrary, the pump power and the required cooling medium flow are maximum.
The coupling of the adjusting movement to the temperature makes possible in advantageous manner to operate with a temperature-sensitive element arranged in the pump wheel hub. The central arrangement is also advantageous from structural point of view, since then the centrifugal forces occurring during the rotation of the pump wheel are transmitted to the temperature-sensitive element only to a low degree.
The temperature-sensitive element in accordance with an advantageous embodiment of the invention can be formed as a growing expansion regulator or a growing motor, with which a linear displacement is possible in dependence on the temperature.
Electrically, hydraulically or pneumatically operated adjusting devices have the advantage that they can be realized with their complex regulation by means of a higher control device, for example with inclusion of the motor control. With the use in the motor vehicles, further optimization potential can be obtained, for example with respect to fuel consumption, exhaust gas emissions, and passenger comfort.
Specifically for cooling of a motor vehicle motor, the adjustability of the radial pump without being dependent from the rotary speed of the control provides additional advantages for optimization of the cooling process. It is advantageous when an adaptation of the pressure difference produced by the pump is possible to the pressure difference required for the cooling system. This is realized in a simple form by a suitable, adjustable slider in the inlet or outlet opening of the cooling medium pump.
The inventive features of the motor-independent adjustability can be realized by other structural approaches, for example by connecting the adjusting device with the vanes of the pump wheel. The connection is designed preferably so that the position of the pump vanes relative to the pump wheel can be changed and the required feeding quantity can be adjusted.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.